In an internal combustion engine, the “ignition system” is the mechanism that ignites the fuel consumed by the engine. Most engines use either an electrical spark or a compression heating ignition system. Typical electrical spark ignition systems rely on a battery, an induction coil, and a spark igniter to provide an electrical spark to ignite the air-fuel mix in the engine's cylinders. Compression heating ignition systems inject fuel into the engine's cylinders and rely on the heat created in the air by compression in the cylinders to ignite the fuel.
In the case of electrical spark ignition systems, the spark igniter is typically a spark plug having electrodes that extend into the combustion chamber. The plug provides a spark and a gap for that spark to jump across. The plug also conducts heat from the combustion process to the cylinder head and into the cooling system.
To meet these performance requirements and to provide long life and superior engine performance, a large amount of technology goes into the design and manufacture of spark plugs. The spark plug manufacturing industry is particularly interested in developing spark plugs that last for longer periods of time.
Currently there is no standard for spark plug durability, Society of Automotive Engineers (SAE) or otherwise. Thus, different manufacturers develop their own standards and tests. For example, many manufacturers have a self-imposed requirement that a spark plug be capable of performing in an automotive engine for at least 100,000 miles before a plug change or tune up is required.
Conventional spark plug testing is achieved by using the spark plugs in a real engine. A typical spark plug test consists of 400 to 500 hours of engine testing running a specified test cycle. An example of a test cycle is 30 seconds at full load followed by 30 seconds at idle, repeated for the test duration. Continuous full load testing is not feasible because of engine durability issues. This method of testing is also expensive because it requires an engine, a dynamometer, and large amounts of fuel.